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hiya! my first post, so be gentle 
(although I have read your forum for a long time).
I got my hands on an old vox ac30 some time ago, and i have some major problems with it.
first off, something about the amp. i don't know which model it is. it's missing the back panel. it's a double speaker version with 2 12' celestion g12m speakers (with gold labels, made in england). tubes are: 4x el84 power tubes, 6 tubes in preamplification and vibrato/tremolo speed control (5x 12ax7 preamp and 1x 12au7 trem). has a diode rectifier. the board is pcb.
i can't find any picture of an ac30 on the net that has the same layout of the controls. i also can't find any schematics that match it completely. this is the closest: http://www.freeinfosociety.com/elect...oxac301986.pdf
mine hasn't got a standby switch or a footswitch (or a footswitch jack).
the previous owner repaired it himself (very poorly). he's a friend of mine, so he told me what he fixed and what was wrong when he got it:
*the tone control was completely disconnected, he fixed it
*brilliance channel inputs were disconected
*the tremolo/vibrato switch was broken
*the mains switch was broken
*some of the caps were broken (split in two!), some even missing (it's possible that he replaced them with wrong ones, because he followed the schematic, and i'm not sure if the schematic is fitting)
*lots of old caps were changed. he changed those two-in-one 450v caps with 2 normal 450v caps
*changed some of the tubes
*rewound the speakers (he had a professional do it)
now, the problems:
1)it blows power tubes
since i got it, it blew two power tubes, both in the same socket. the tubes were destroyed by heat i think, both broke above the same pin, which is connected to output transformer. it even melted the plastic tube socket, so i changed it for a ceramic one. it didn't stop it from blowing the tube again. the tube in that socket shines much brighter than the others, too. when i remove that tube and the one in it's pair (put it on half power), the one from the other pair, that's close to the glowing one starts glowing really bright, almost blue, too.
2)the brilliance channel is screwed
first off, it really doesn't like pedals in the lower input. the second thing is that, after a few minutes, it just stops playing. it comes back on for a few seconds when i move the brilliance pot or take out the cable from the input and put it back in, and then it stops playing again. in the upper output, it plays for a bit longer and then it stops. it also gives the speakers some awful low-end speaker fluttering distortion, when really turned up. it seems to have way too much gain, too
3)the vibrato/tremolo channel
it has almost no or no effect. when the guitar is connected to vibrato/tremolo channel, the sound is okay, low gain, but it has no vibrato or tremolo, no matter what speed settings i choose, both for vibrato and tremolo.
4)cosmetics
it's missing the vox sign, some of the knob covers are from a bassman, it's missing the handles. anyone know where to find these cheap in europe?
5)the back plate
it's missing. anyone have a picture, so i can make one?
possible causes:
1) 220/110 mains switch is bypassed, and the power transformer is hard wired to the fuse holder, so my friend may have soldered the wrong wire
2) he may have connected the speakers to the wrong impedance output of the output transformer
3) he didn't have the right schematics, so the condenser values of the replaced missing caps may be wrong
4) the vibrato/tremolo switch is replaced poorly
pictures:
(although I have read your forum for a long time).I got my hands on an old vox ac30 some time ago, and i have some major problems with it.
first off, something about the amp. i don't know which model it is. it's missing the back panel. it's a double speaker version with 2 12' celestion g12m speakers (with gold labels, made in england). tubes are: 4x el84 power tubes, 6 tubes in preamplification and vibrato/tremolo speed control (5x 12ax7 preamp and 1x 12au7 trem). has a diode rectifier. the board is pcb.
i can't find any picture of an ac30 on the net that has the same layout of the controls. i also can't find any schematics that match it completely. this is the closest: http://www.freeinfosociety.com/elect...oxac301986.pdf
mine hasn't got a standby switch or a footswitch (or a footswitch jack).
the previous owner repaired it himself (very poorly). he's a friend of mine, so he told me what he fixed and what was wrong when he got it:
*the tone control was completely disconnected, he fixed it
*brilliance channel inputs were disconected
*the tremolo/vibrato switch was broken
*the mains switch was broken
*some of the caps were broken (split in two!), some even missing (it's possible that he replaced them with wrong ones, because he followed the schematic, and i'm not sure if the schematic is fitting)
*lots of old caps were changed. he changed those two-in-one 450v caps with 2 normal 450v caps
*changed some of the tubes
*rewound the speakers (he had a professional do it)
now, the problems:
1)it blows power tubes
since i got it, it blew two power tubes, both in the same socket. the tubes were destroyed by heat i think, both broke above the same pin, which is connected to output transformer. it even melted the plastic tube socket, so i changed it for a ceramic one. it didn't stop it from blowing the tube again. the tube in that socket shines much brighter than the others, too. when i remove that tube and the one in it's pair (put it on half power), the one from the other pair, that's close to the glowing one starts glowing really bright, almost blue, too.
2)the brilliance channel is screwed
first off, it really doesn't like pedals in the lower input. the second thing is that, after a few minutes, it just stops playing. it comes back on for a few seconds when i move the brilliance pot or take out the cable from the input and put it back in, and then it stops playing again. in the upper output, it plays for a bit longer and then it stops. it also gives the speakers some awful low-end speaker fluttering distortion, when really turned up. it seems to have way too much gain, too
3)the vibrato/tremolo channel
it has almost no or no effect. when the guitar is connected to vibrato/tremolo channel, the sound is okay, low gain, but it has no vibrato or tremolo, no matter what speed settings i choose, both for vibrato and tremolo.
4)cosmetics
it's missing the vox sign, some of the knob covers are from a bassman, it's missing the handles. anyone know where to find these cheap in europe?
5)the back plate
it's missing. anyone have a picture, so i can make one?
possible causes:
1) 220/110 mains switch is bypassed, and the power transformer is hard wired to the fuse holder, so my friend may have soldered the wrong wire
2) he may have connected the speakers to the wrong impedance output of the output transformer
3) he didn't have the right schematics, so the condenser values of the replaced missing caps may be wrong
4) the vibrato/tremolo switch is replaced poorly
pictures:
) In any case, you' ll simply need to use Ohm's law to suit the voltage drop to your needs ( R=Desired voltage drop / Current flowing in Amps ) and to properly size the resistors' power rating ( Pd=Voltage drop across the resistor you're sizing * current in Amps flowing ). 
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